Reduced SCR catalyst efficiency; Poor-quality AdBlue or dosing faults; Faulty NOx sensor; EGR system faults increasing engine-out NOx; Exhaust leaks affecting sensor readings.

NOx sensors

P2BAD NOx Exceedance - Root Cause Unknown

Q: What does P2BAD mean?

NOx Exceedance - Root Cause Unknown. The ECU monitors NOx emissions, mainly through the downstream NOx sensor, and compares them with the permitted limits. P2BAD is set when NOx emissions are too high and the system cannot attribute the cause to a specific component.

The ECU monitors NOx emissions, mainly through the downstream NOx sensor, and compares them with the permitted limits. P2BAD is set when NOx emissions are too high and the system cannot attribute the cause to a specific component.

Common causes

Reduced SCR catalyst efficiency
Poor-quality AdBlue or dosing faults
Faulty NOx sensor
EGR system faults increasing engine-out NOx
Exhaust leaks affecting sensor readings

Typical symptoms

Check engine light and/or emissions warning on
Countdown to engine start restriction on many vehicles
Reduced power or limp mode

P2BAD and NuoVolta

When the SCR/AdBlue or EGR system has been removed or disabled for off-road or motorsport use, where permitted by law, the matching NuoVolta solution (AdBlue / SCR / NOx Removal or EGR Removal) adjusts the ECU calibration and the DTC removal feature can disable this code. Because the root cause is unknown, a full diagnosis is recommended on a vehicle with intact systems.

AdBlue / SCR / NOx Removal Available for 121 ECUs EGR Removal Available for 256 ECUs

Related codes

P2200NOx Sensor Circuit (Bank 1 Sensor 1) P2201NOx Sensor Circuit Range/Performance (Bank 1 Sensor 1) P229FNOx Sensor Circuit Range/Performance (Bank 1 Sensor 2)

Diagnose and repair real faults first. Removing or disabling emission systems is only permitted where allowed by law, for example for off-road or motorsport use.